Cross-bar type, impulse responsive, telephone switching apparatus



July 2, 1957 CROSS-BAR Filed Aug. 15, 1955 K. w. GRAYBILL ET AL TYPE,IMPULSE RESPONSIVE, TELEPHONE SWITCHING APPARATUS 2 Sheets-Sheet 1INVENTORS. KENNETH w. GRAYBILL mus ssnesauscn ATTY.

July 1957 K. w. GRAYBILL ET AL 2,798,119

CROSS-BAR TYPE, IMPULSE RESPONSIVEJ, TELEPHONE SWITCHING APPARATUS FiledAug. 13, 1953 2 Sheets-Sheet 2 E IE iI I 2 u.

I2 R E '0 k m o a om (O u 3 m 9' g o o g I; LL Q ,9, 23

INVENTORS. Q g xzrmzm w. GRAYBILL HANS SEN esuscn BY 6 I ATTY.

United States CROSS-BAR TYPE, IMPULSE RESPONSIVE, TELEPHONE SWETCHENGAPPARATUS Kenneth Wayne Graybill, Elmhurst, and Hans Sengebusch,Chicago, 1111., assignors to General Telephone Laboratories,Incorporated, a corporation of Delaware Application August 13, 1953,Serial No. 374,016

8 Claims. (Cl. 179--27.54)

The present invention relates in general to automatic telephoneswitching apparatus and in particular to pulse operated switches of thecross-bar type wherein a plurality of subscribers line circuits, ortrunks, associated with a multiple field of bare conductors, are madeaccessible through any one of a group of such switches to a local oroutgoing trunk individual to the switch, for extending telephoneconnections. It is an improvement on the switches illustrated anddescribed in our prior Patent 2,680,783, issued June 8, 1954.

In the referred to prior application, each switch was provided with aprimary shaft and ten secondary shafts at right angles to the primaryshaft and all in the same plane. The primary shaft carried ten bevelgears mounted at regular intervals along its length, and each secondaryshaft had a similar bevel gear mounted on one end thereof, adjacent toone of the gears on the primary shaft, but normally disengagedtherefrom. An impulse responsive motor device was arranged to drive theprimary shaft alone in a first selecting movement to select one of saidsecondary shafts for operation. At the end of the primary rotation, atrigger bar carrying a plurality of pivoted triggers, or bell cranklevers, was pulled lengthwise by an electromagnet whereupon one of thetriggers was caused to rock on its pivot, and lift the selected shaftand its bevel gear into engagement with the corresponding bevel gear ofthe primary shaft. A second operation of the driving motor then caused afurther rotation of the primary shaft, and a corresponding rotation ofthe engaged secondary shaft. The rotation of the secondary shaft thencaused one of a plurality of sets of flexible contact fingers to bemoved into engagement with a corresponding set of bare conductors toextend a connection between the trunk individual to the switch and aparticular one of the line or trunk circuits associated with said bareconductor multiple.

The main feature of the present invention is the elimination of theprimary shaft and the bevel gears, and'the provision instead of a simplespur gear drive of ten gears directly mounted on the secondary shafts.These gears are permanently meshed with one another and are freelyrotatable about their respective shafts. Both the cost and the number ofthe gears is thus reduced, and the problem of meshing and unmeshing ofgears is completely eliminated.

Another feature of the invention is the means whereby the secondaryshaft selected by a first movement of the gear train, is positivelylocked to its gear, for rotation therewith.

Other features of the invention will be made apparent by the followingspecification and claims, when considered together with the appendeddrawings comprising Figures 1 to 9 inclusive.

Fig. 1 represents a top or plan view of one of the switches, with twoshafts shown in full, and the others shown only in part, as they aresimilar to those shown.

Fig. 2 is an inverted side view of the gear train, from the trigger barside, with all intervening and other parts 2,798,119 Patented July 2,1957 omitted, to show certain details. In this view the gear train isshown in the normal, unoperated position.

Fig. 3 is an enlarged sectional view taken along the line A-A in Fig. 1,and including a portion of a second switch assumed to be below theswitch of Fig. 1.

Fig. 4 is an enlarged plan view of the upper left corner of Fig. 1,showing the left trigger bar actuated and the left shaft locked to itsgear, for rotation thereby.

Fig. 5 is an enlarged side view of the left three gears of the geartrain, seen as in Fig. 2, but in position to select the left shaft foroperation, in accordance with Fig. 4.

Fig. 6 shows a side view in elevation of a row of flexible contact setsas assembled into the switch, but with all intervening and associatedparts removed.

Fig. 7 represents a top view of the contact sets of Fig. 6.

Fig. 8 represents an end View in elevation of the contact sets of Fig.6, to which has been added an end view of a section of the bareconductor field associated therewith, and an end view of the associatedcontact actuators, which urge the flexible contact sets into engagementwith the corresponding bare conductors in response to the rotation ofthe associated shaft.

Fig. 9 is a side view in elevation of a portion of one of four partscomprising Fig. 6.

A complete assembly of switches, which may be used as linefinders,selectors, or connectors, consists of a plurality of switches such asshown in Fig. 1, mounted one above the other on an arrangement ofvertical bare conductors, which are common to all of the switches of thegroup.

The bare conductor multiple, or field, comprises a plu-. rality ofpanels 26, mounted parallel to each other, and

spaced at regular intervals to provide room for the shafts andactuators. Fig. 1 provides for a total of ten such panels, of which onlythe first and last have been shown completely, since they are allsimilar. Each panel 20 consists of a channel plate 19 mounting a numberof transverse slotted insulators, not shown, one above the other, in theslots of which the required number of vertical bare conductors 22 havebeen inserted and locked in place in any suitable manner. One end ofeach channel plate is secured to a back plate 11, and the other end to afront plate 14 in any suitable manner, as by the screws indicated.

In Fig. 1 each panel 20 is indicated as having 40 vertical bareconductors 22, which may be assumed to represent ten sets of fourconductors each, connected to line circuits or trunks as required. Itwill be obvious that the complete multiple will include 400 such bareconductors corresponding to lines or trunks divided into ten groups often. It will also be obvious that more or less than four conductors perline or trunk, and more or less than forty per panel, may also beprovided.

Horizontally disposed across each row of vertical bare conductors and inalignment therewith, in each switch, is a row of 40 flexible contactfingers, best seen in Figs. 6, 7, 8, 9. The complete assembly consistsof four horizontal, spring-metal fiat conductors 35', 36, 37, 38,mounted one above the other in a suitable insulating mounting not shownin Figs. 6-9 but indicated at 30 in Figs. 1 and 3. Depending from eachhorizontal con ductor are ten spaced apartvertical contactfingers 39,each such conductor and its contact fingers being stamped and formedfrom a single piece of metal. The vertical contact fingers of the fourconductors are staggered or arranged in 1, 2, 3, 4 order, in groups offour, as best seen in Fig. 6, so as to enable the four conductors tomake contact with any set of vertical bare conductors 22 in the row, bymoving the corresponding set of four contact fingers against them. Thefour metallic parts forming this assembly are similar, butnot identical.

The free ends 40-43 of each group of four horizontal conductors (Figs. 3and 6) extend, in the final assembly, beyond the back plate 11, wherethey may be multipled, in any convenient manner, with the other ninegroups of similar conductors of the same switch, to form a single 4-wiretrunk having access to any set of vertical bare conductors associatedwith such switch, through the various sets of contact fingers thereof.

The formed, downwardly extending contact fingers 39 are so formed andtensioned that in the normal unoperated position, the free tips 13 (Fig.8) are adjacent to, but clear of, the corresponding bare conductors 22.Thus when any contact finger is moved a short distance in a clockwisedirection, its tip 13 will be pressed into sliding contact with theassociated conductor 22, and will establish an electrical connectiontherewith.

Horizontally disposed across each row of contact fingers, and in contacttherewith, is a row of ten contact actuators 34 (Figs. 1, 3, 8). Eachsuch actuator consists of a rectangular insulating plate, of a width toactuate four contact fingers, and suspended loosely from an upperbracket on the frame, as by a series of'lugs 31 (Fig. 3) extendingthrough slots in the actuators. Thus when any contact actuator 34 isurged in a clockwise direction, it will move the associated four contactfingers 39 into engagement with the corresponding four vertical bareconductors 22. The contact actuators 34 may be of insulating materialwith vertical slots on the inner face to receive the contact fingers andprevent them from moving sideways, or they may be made of metal with acontact centering comb or nest of insulating material mounted on theinner face.

Horizontally disposed across each row of contact actuators, and inproximity thereto, is a cam shaft 60, slidably mounted in suitablebearings in the plates 11 and 14. These shafts, as shown in Fig. 1, areeach provided with ten spaced cams 64 for operating the associatedcontact actuators, and an off-normal cam, seen at the lower end, foroperating a set of oflF-normal contacts 63, which may be varied innumber and arrangement as necessary. The single high points of thedilferent cams are spirally distributed around the circumference of eachshaft in eleven equal steps, so that the associated olfnormal springswill be actuated by the last cam when the shaft is in the normalposition, while the associated contact actuators will be operated insuccession by the other cams at each one-eleventh of a revolution, whenthe shaft is rotated away from its normal position.

A spring 74, in engagement with the lower end of each shaft as seen inFig. 1, urges the shaft upwardly. In the normal position of the shaft, apin 72, projecting upwardly from a hub 71 secured to the shaft near itsupper end just inside the back'plate 11, is forced into a hole notshown, in the back plate 11, and enables the shaft to move axially inits bearings to the position shown in Fig. 1. In this position the pin72 effectively locks the shaft against rotation.

A spur gear .70 is loosely mounted on the upper end of each shaft, onthe outer side of the back plate 11. These gears, in addition to beingfreely rotatable about their shafts, are permanently meshed with eachother to form a gear train, as shown in Figs. 1 and 2. Each gear 70 isprovided with an inner hub 73 which rides on the back plate 11, and anouter hub 74, which is provided with a slot 75 cut across the flat outerface thereof. The outer face of each gear 70 is also provided with astud 76 near the outer periphery, and in line with the slot in the hub74. A pin 61 is also inserted crosswise in each shaft 60 near the upperend thereof, with a portion projecting on each side of the shaft, justclear of the outer hubs 74 of the gears 70. In the normal position ofthe shafts, these pins all point in the same direction, lengthwise ofthe gear train. They provide the means for locking the shaft toitsassociated gear, for operation thereby, as will be shown.

Mounted lengthwise of the gear train and just beyond the pin end of theshafts, is a trigger bar 80, slidingly mounted on a back angle of backplate 11, so as to be movable longitudinally in either direction. As maybe seen in Figs. 3 and 4, the trigger bar or slide bar 80 is looselymounted on a row of posts 81 by a number of button-head screws 82inserted through slots 83 in the trigger bar, into threaded holes in theends of the posts 81. One end of the trigger bar 80 is loosely securedto the free end of the armature 91 of a transfer magnet 90, also mountedon the back plate 11. A restoring spring 92 on the magnet 90 normallymaintains the armature 91 and the trigger bar 80 in their right hand,unoperated position shown in Fig. 1. The trigger bar 80 is also arrangedto operate a set of contact springs 93, by means of the slope 94 and theroller 95, each time the electromagnet 90 is operated to pull thetrigger bar to the left.

A row of ten bell crank levers or triggers 84 are mounted at regularintervals along the trigger bar 80, on pivots 85, opposite the upper endof each shaft. These triggers are'normally held against the stops 77, inthe position shown in Fig. 1 by the coil springs 86, which are securedat one end to a projection on the trigger, and

at the other to a screw 87 on the trigger bar 80. In this position onearm of each trigger has its tip adjacent to the upper end of theassociated shaft 60, while the tip of the other arm is adjacent to theouter face of the associated gear 70, near the periphery thereof, justbeyond the arc of travel of the studs 76 when these rotate with theirrespective gears.

The impulse responsive motor which drives the gears 70, is shown at 50on the right of Fig. 1. It may be of any desired type that will drive ashaft a given distance in a uniform direction for each complete impulsereceived, or that responds in a positive manner to both the make and thebreak of each impulse. In the illustrated embodiment, it is assumed tobe of the general type shown and described in British Patent 649,427,published January 24, 1951, wherein a shaft such as 51 is rotated aquarter turn on each energization of a coil 52, and is rotated anotherquarter turn in the same direction on each de-energization of the coil.Upon each energization also, a cam such as the butterfly cam 53 carriedby the shaft, operates 'a set of contacts of any desired arrangement,such as shown at 54, 55. The cam 53 also returns the contacts 54, 55 tothe normal position shown on each subsequent de-energization of the coil52.

The motor shaft 51 is arranged by means of suitable gearing to drive thegears 70 one-eleventh of a revolution for each half revolution of theshaftSl, through the intermediary of a driving gear 58 (Fig. 2). Apinion 59 on the gear 58 also serves to drive an off-normal gear 65either one or two revolutions for each revolution of the gears 70, asdesired. In the illustrated embodiment, it is assumed that .the gearratio'is such that the gear 65 makes one revolution for each tworevolutions of the gears 70. The gear 65, which is loosely mounted on ashaft or spindle 66 rigidly secured to the back plate 11, carries arelease stud 67 on its outer face near the periphery (Figs. 1, 2), andan off-normal stud 68 (Fig. l) on its inner face, in the same relativelocation. In the normal position of the gear train, these studs occupythe radial position shown for stud 67 in Fig. 2. In this position, thestud 68 is pushing apart a pair of off-normal springs 98, and the stud67 is under one end of a latch 88, which is pivoted at 69 on anextension of the shaft 66. The left end of the latch 88 is thereby heldin place directly below the rightend of the trigger bar 80, against thetension of a coil spring 89 which tends to rock the latch 88 on itspivot in a clockwise direction.

Considering again the gear train for the cam shafts as shown in Fig. 2,the seemingly aimless arrangement of the studs 76 on the gears 70, isdue to the fact that each gear revolves in a direction opposite to thatof its immediately neighboring gear or gears. The gears 70, like thegear 65, are shown. in the normal position, and for -'convenience, havebeen numbered 1 to 10, from right to left. With reference to the variousarrows indicating the direction of rotation, it will be apparent thatafter the .gears 70 have made one-eleventh part of a completerevolution, gear number 1 on the right will have rotated one step orone-eleventh revolution in a clockwise direction. In this position ofthe gear train, the stud 76 of gear number 1 will be directly on thecenter line of the gear train on the right side of gear number 1, and noother stud 76 will be in a corresponding position. Similarly, aftertwo-elevenths of a revolution, gear number 2 will have rotated two stepsin an anti-clockwise direction, and will have moved its stud 76 to thecenter line of the gear train on the right side of gear number 2. Noother stud 76 will then be in a corresponding position, gear number 1having of course moved its'stud hey-ond the center line on the secondstep. Each gear will similarly align its stud 76 in turn on successivesteps, to select the corresponding shaft for operation, only one studbeing on the center line at any given time, with none in line when thegear train is in the normal position. On the first step of the geartrain also, the off-normal cam 65 rotates the stud 67 in a clockwisedirection clear of the right end of the latch 88. The left end of thelatch 88 is thereupon pulled up against'the bottom of the right end oftrigger bar 80, by the coil spring 89. At the same time, the stud 68 ofcam 65 is moved away from the off-normal springs 98 which thereuponclose. It will be understood that a larger number of off-normal contactsmay be employed, if necessary, in any desired arrangement.

Proceeding now to the operation of the switch, let it be assumed thattwo series of ten impulses each are received by the motor 50, with ashort pause between the two series. In response to the first series often impulses, the motor 50 drives the gears 70 ten steps, ortenelevenths of a complete revolution. Stud 76 of gear number isaccordingly moved ten steps in an anticlockwise direction as indicatedby the arrow, and is thereby placed in the selecting position on theright side of the gear along the center line of the gear train. See Fig.5. In this position the stud 76 of gear number 10 is directly in thepath of the lower arm of the associated trigger 84, and the slot 75 ofthe same gear is aligned with the pin 61 of the corresponding shaft.None of the other slots 75 or studs 76 are so aligned. i J During thepause following the first series of impulses, the transfer magnet 90 isenergized, in any convenient manner, and attracts its armature 91. SeeFig. -4. Trigger bar 80 is therebydrawn to the left, whereupon the tipof the lower arm of the left trigger 84 strikes against the aligned stud76 of gear number 10. The said trigger 84 is thereby rocked in ananti-clockwisedirection, forcing the upper arm down against the end ofthe number Ill-shaft 60. This shaft is accordingly moved longitudi:nally, and the pin 61- of this shaft is pushed down into the alignedslot 75. At 'the same time, the pin 72 of the shaft hub 71 is moveddownward out of the associated hole, not shown, in back plate 11, and ismoved into a position just'clearing the inner surface of back plate 11.The selected shaft is now locked to its gear for rotation thereby, andis also unlocked from the frame of the switch, to permit such rotation.The leftward movement of the trigger bar also causes the roller 95 toride upon the shoulder 94 of the trigger bar, which in turn causes theoperation of the contact springs 93, which like the other contacts, mayvary in number and arrangement as required.

Upon the first movement of the gear train, the right hand gear 65(Fig. 1) releases the gear train off-normal contacts 98 and the latch88, as previously described. When therefore, trigger bar 80 is pulled tothe left, the latch 88 is rocked in a clockwise direction and the stepin the left end of the latch is pulled up into place against the rightend ofthe trigger bar by the latch spring 89, thus effectively lockingthe trigger bar and the magnet armature 91 in the operated position. Thesubsequent deenergization of the magnet is consequently without effect.

The motor 50, in response to the second series of ten impulses, nowdrives the gear train an additional ten steps. The selected shaft number10 is also driven ten steps or ten-elevenths of a revolution, by thelocked-on gear number 10. Upon the initial movement of the shaft, thepin 72 of the shaft hub 71 is rotated away from the associated hole inback plate 11, and rides on the inner surface of the back plate 11. Uponthe initial movement of the shaft also, the stud 76 of the associatedgear is moved clear of the trigger 84, which is thereupon pulled backinto the upright position against the stop 77 by the trigger spring 87.The selected shaft number 10 however, is now maintained in its downwardlocked position by the pin 72 riding on the plate 11.

Upon the first step of the locked shaft, the off-normal cam at the lowerend of the shaft releases the off-normal springs, and the first cam atthe upper end of the shaft engages the associated contact actuator andcauses the latter to move the associated four contact fingers intoengagement with the corresponding vertical bare conductors. Upon thesecond step of the shaft, the second cam will operate its contactactuator and the first cam will release its contact actuator, which willbe returned to the normal position by the back tension of the associatedcontact fingers. The other contact actuators will be operated insuccession in similar manner, so that upon the completion of the seriesof ten impulses, the tenth contact actuator and the associated contactfingers will be operated, and all of the others will be normal. Aconnection is thereby extended to the 00 line or trunk, or the tenthline or trunk in the tenth group of ten lines or trunks. It will beobvious from the foregoing that any shaft or group may be selected,depending on the number of impulses in the first series received by themotor 50, and that any line or trunk in the chosen group may beselected,depending on the number of impulses in the second series received by themotor.

Release of the switch may be effected by closing a circuit to the motorin any convenient manner, through the gear train off-normal contacts 98and the motor interrupter contacts 55 in series. When this circuit isclosed, the motor is energized and advances the gear train. 1 It alsocauses cam 53 to open the interrupter contacts 55,- and the motor isaccordingly de-energized to again advance the gear train. Cam 53 thenallows interrupter contacts 55 to re-close, and this action continuesuntil the gear train has been returned to its normal position, whenoff-normal springs 98 are opened by stud 68 to stop the rotation. At thesame time, stud 67 lifts up the right end of latch 88. This drops theleft end of latch 88, which disengages itself from the right end of thetrigger bar 88. Since the magnet 90 is de-energized at this time, coilspring 92 then moves armature 91 and trigger bar 80120 the right, backto their normal position as shown in ig. 1.

Since it has been assumed that the ofi-normal gear 65 makes onerevolution for each two revolutions of the gears 70, it will be obviousthat any operated shaft 60 will reach its normal position before thegear 65 will have been returned to its normal position. When theoperated shaft completes its rotation, its pin 72 is pressed into theassociated hole in back plate 11, and the shaft is moved into its upperposition, by the pressure of spring 74, disengaging the pin 61 from theslot 75. The shaft is now once again locked in the normal position, freeof its associated gear, and the shaft ofiF-normal contacts 63 are againoperated. The gear train will then continue its rotation free of theshafts, and restore the trigger bar and the switch to normal, asdescribed in the preceding paragraph.

7 A m difi at 9. th e ase or ra n may e p ovit ss i de i e y abus n thsea ratio o sca 6.

so that it completes its rotation in the same time as the gears 70, andby connecting off-normal contacts 98 in mnltiple with a pair of similaroff-normal contacts on each shaft. With such a gear arrangement, thegear train would reach its home position first, whenever the sum of thetwo series of received impulses did not exceed eleven. In such case, thearrival of the gear train at the home position, would cause stud 67 totrip latch 88, and enable trigger bar 80 to resume its right handposition. Since no studs 76 would be aligned at this time, this movementwouldbe unimpeded. The operated shaft would likewise be uneffected, asits pin 72 continues to hold it in the gear-locked position. Contacts 98would also open, but without eifect, as these contacts would still beshunted by the still closed shaft-otf-normal contacts. The gear trainwould thus continue to rotate and proceed to make a second revolution.The restoration and disengagement of the operated shaft would becompleted during the second rotation of the gear train. And whenoff-normal contacts 98 subsequently opened again, at the completion ofthis second rotation, the gear train would simply stop. If however, thesum of the two series of received impulses were greater than 11, theoperated shaft would reach its home position first, in which case therelease would be as in the preceding paragraphs, except that there wouldbe no second rotation of the gear train.

What is claimed is:

1. In an automatic switch, a plurality of rows of parallel bare wireconductors, a row of sets of contact fingers for each row of conductors,a shaft for each said row of contact sets, cams along said shafts foroperating the sets of contact fingers of the row successively intoengagement with the corresponding conductors in response to rotation ofsaid shaft, a gear train comprising a gear mounted on each shaft, saidgears being permanently meshed together and freely rotatable about theirrespective shafts, a motor for rotating all of said gears in a firstmovement, selecting means positioned in response to said first movementof said gear train to select any one of said group shafts for operation,a coupling means, a magnet for operating said coupling means, meansoperated responsive to said operation of said coupling means for movingthe selected shaft axially, and means responsive to said axial movementfor locking said selected shaft to its associated gear to enable saidselected shaft to be rotated in response to a second movement of saidgear train by said motor for operating any one of the associated sets ofcontact fingers.

2. An automatic switch as in claim 1 including, a normally disengagedkey and keyway for each said shaft and gear, and said keys and keywaysso located radially as to cause the engagement of the associated key andkeyway, responsive to said axial movement of said selected shaft, toenable the associated gear to rotate said selected shaft.

3. In an automatic switch as in claim 1, a frame for said switch, afirst lug for each shaft normally engaged by said frame, a secondnormally disengaged lug for each shaft, and openings in said frame andsaid gears so disposed as to enable disengagement of said first lug fromsaid frame and engagement of said second lug with the associated gearresponsive to said axial movement of the selected shaft, to enablerotation of said shaft by said associated gear.

'.In r ss a swi ch, a plur li y o para ro 9. naralle b nk conducto s; arowof sets er fingers across each said'row -,o f conductors, ash'aftacross each said row of contact fingers, a spur gear mounted on andfreely rotatable about the end of .each said shaft, each said gearpermanently meshed with the next, a motor for driving said gears inresponse to received impulses, a movable bar overlaying one end of .saidshafts, a pivoted trigger on said bar overlaying the same end of eachshaft, a stud .on each gear so located that one of said studs will bealigned with one of said triggers to select one ofsaid shafts foroperation in accordance with the value of a first series of receivedimpulses, an electromagnet for moving said bar and said triggersfollowing said selection to cause said aligned stud to rock said onetrigger against the end of said selected shaft to move said shaftaxially, locking means operated responsive .to said axial movement forlocking saidselected shaft .to its gear to enable said motor to rotatesaid shaft responsive to a second series of received impulses, and camson said shaft for operating any one of the associated sets of contactfingers into engagement with the corresponding bank conductors, inaccordance with the value of said second series of impulses.

5. In a cross-bar switch as in claim 4, a cross-pin for each shaft, ahub for each gear, and a groove in each hub in such a location as to bealigned with the associated shaft pin when the stud of said gear isaligned with the associated trigger, to enable said pin to engage saidslot when said shaft is moved axially by said trigger.

6. In a cross-bar switch as in claim 4, a pin inserted transversely ineach shaft near the end thereof, a hub for each said gear, a grooveacross said hub on the side facing said pin, and said pin and groove solocated with respect to the associated stud of said gear as to causeengagement of the pin of the selected shaft in its associated groovewhenever said shaft is moved axially through the coeoperation of theassociated stud and trigger bar.

7. In a cross-bar switch as in claim 4, a pin crosswise through the endof each shaft and normally in alignment with said triggers, a hub foreach gear, and a slot across said hub in alignment with the stud of saidgear for receiving said pin responsive to said axial movement of saidshaft to rotatively couple said shaft with said gear.

8. In an automatic switch, aplurality of parallel rows of parallel bareconductors, ,a row of movable contact sets facing each said row ofconductors, a shaft facing each said row of contact sets, means formoving the associated contact sets into contact with the associatedconductors responsive to rotation of said shafts, agear loosely mountedon each shaft near one end, said gears being permanently in mesh to forma gear train, a motor for rotating said gears in response to a firstseries of received impulses, means responsive to said gear rotation forselecting one of said shafts for rotation, a slide bar, a magnet formoving said slide bar lengthwise, means responsive to said movement ofsaid slide bar for moving said selected shaft axially under control ofsaid selecting means, normally misaligned locking means for saidselected shaft and its associated gear rotated into alignment responsiveto said first rotation of said gears, and said aligned locking meansengaged responsive to said lengthwise movement of said selected shaftfor rotatively connecting said selected shaft to said associated gearfor rotation thereby responsive to a subsequent series of receivedimpulses.

No references cited.

